1. Field of the Invention
The present invention relates to a low dropout regulation system and an operation method of a low dropout regulation system, and particularly to a low dropout regulation system and an operation method of a low dropout regulation system that can immediately respond to variation of an inner output voltage.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a low dropout regulator 100 according to the prior art. The low dropout regulator 100 includes a P-type metal-oxide-semiconductor transistor 102, an operational amplifier 104, a first resistor 106, and a second resistor 108. As shown in FIG. 1, the P-type metal-oxide-semiconductor transistor 102, the operational amplifier 104, the first resistor 106, and the second resistor 108 generate and output an inner output voltage VINT according to a reference voltage VREF and equation (1), where the operational amplifier 104 can regulate the inner output voltage VINT according to the reference voltage VREF through the P-type metal-oxide-semiconductor transistor 102.VINT=VRE*[(R1+R2)/R2]  (1)
As shown in equation (1), R1 is a resistance of the first resistor 106 and R2 is a resistance of the second resistor 108. However, because the low dropout regulator 100 utilizes the P-type metal-oxide-semiconductor transistor 102 to be a driving device, and utilizes the operational amplifier 104 to regulate the inner output voltage VINT according to the reference voltage VREF, the low dropout regulator 100 has disadvantages as follows: first, if a load 110 coupled to the low dropout regulator 100 needs a large transient current, the operational amplifier 104 can not immediately respond to regulate the inner output voltage VINT and the P-type metal-oxide-semiconductor transistor 102 cannot immediately provide the large transient current, resulting in the inner output voltage VINT being quickly decreased; second, if a capacitance of the load 110 coupled to the low dropout regulator 100 is too small, the low dropout regulator 100 has bad zero/pole compensation, resulting in the low dropout regulator 100 being unstable; and third, if the low dropout regulator 100 operates in a supply voltage VDD with large variation, the low dropout regulator 100 can not provide a fixed driving current to the load 110.